1. Field of the Invention
The present invention relates to fuel cell systems and methods for controlling the same. More specifically, the present invention relates to a fuel cell system which circulates a supply of aqueous fuel solution to an anode of a fuel cell, and a method of controlling the fuel cell system.
2. Description of the Related Art
Recently, there has been a desire in the field of direct methanol fuel cell systems that the time from start-up to full power generation should be shortened. As one solution, it has been disclosed to shorten a temperature rise time in which the aqueous methanol solution supplied to the fuel cell reaches a predetermined temperature.
For example, JP A 2004-55474 (Patent Document 1) discloses a technique in which a temperature raising device is provided between a fuel storing portion and a cell stack, and a portion of the aqueous methanol solution in the fuel storing portion is supplied to the temperature raising device at the time of start-up, thereby increasing the temperature of the aqueous methanol solution. The temperature raising device includes a platinum catalyst, and generates heat through a chemical reaction process involving oxidization when the aqueous methanol solution is brought into contact with the platinum catalyst and air.
The technique disclosed in Patent Document 1 enables a quick temperature rise of the aqueous methanol solution which is to be supplied to the fuel cell. However, a portion of the aqueous methanol solution is oxidized, which reduces the utilization efficiency of the methanol.